Cosmological density parameter
= Cosmological density parameter
{title2=$\Omega$}
The density parameter is $\Omega=\rho/\rho_{\rm crit}$. In a Friedmann universe, its departure from one measures the spatial-curvature term relative to the density or expansion term.
The <Friedmann equation> relates this ratio to spatial curvature and the expansion rate; the parameter and the evolution equations are distinct concepts.